Analog Devices UG-065 User Manual

Evaluation Board User Guide
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UG-065
iMEMS ADXL345 Inertial Sensor Datalogger and Development Board
FEATURES
Ultralow power ADXL345 accelerometer Inertial sensor development board Datalogs onto MicroSD card Fully programmable via serial interface; firmware examples
provided
Battery-powered for portable applications
REQUIREMENTS
2 AAA batteries MicroSD card and card reader (for datalogging) Computer with serial port (for programming)
Figure 1. Inertial Sensor Development Board
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GENERAL DESCRIPTION
It is often a time saver in hardware development to make progress on the firmware and the hardware simultaneously. The challenge is that it proves difficult to develop firmware before the hardware exists. The iMEMS® ADXL345 development board is an easy­to-use tool that facilitates prototyping by providing a platform that can be duplicated in the final application. Additionally, the development board can be configured as a datalogger and can be used to gather data for refining algorithms, tuning thresholds, and generally familiarizing oneself with accelerometer data.
Two AAA batteries power the development board and thus it integrates seamlessly into portable applications. Communications and processing is done by an ARM7-based ADuC7024 micro­controller, and the interface provided is fully reprogrammable. Moreover, all ADuC7024 pins are broken out into headers to facilitate design of compatible expansion boards. Data is logged onto a MicroSD memory card, providing essentially unlimited memory capacity and operating system versatility. Data is stored in a text file; therefore, there is no need to install any software to operate the board or read data. Software is provided to assist with programming the board.
Please see the last page for an importan t warning and disclai mers.
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TABLE OF CONTENTS
Features.............................................................................................. 1
Requirements .................................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Overview............................................................................................ 3
Features.......................................................................................... 3
Using the Board ................................................................................ 4
REVISION HISTORY
2/10—Revision 0: Initial Revision
Getting Started...............................................................................4
Programming the Board...............................................................4
Software Tools................................................................................4
Board Layout and Schematics..........................................................6
ESD Caution...................................................................................8
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(A) RESET
AND PROG RELEASED
(B) PUSH PROG
(C) PUSH RESET
OVERVIEW
The ADXL345 inertial sensor development board has the following features:
A 2-layer printed circuit board (PCB), 1.125-inches × 2.25­inches form factor
A two AAA battery power supply
A 4-pin UART header to connect to RS232 interface cable
Reset/download push-buttons
Power indicator/general-purpose LEDs
Access to all microcontroller I/Os from the external header; all device pins are brought out to the external header pins
Demonstration firmware
FEATURES
Power Supply
A pair of AAA batteries powers the board, and the battery holder is located on the back of the board. An on/off switch on the lower left of the front of the board controls power to it. The battery voltage is not regulated but is decoupled with a 10 µF capacitor globally, and an additional 1 µF capacitor at the device supply pins to ground.
RS232 Interface
The ADuC7024 (UC1) P1.1 and P1.0 lines are connected to the RS232 interface cable via the connector (UART). The interface cable generates the required level shifting to allow direct connection to a PC serial port. Ensure that the supplied cable is connected to the board correctly, that is, VDD is connected to VDD and GND is connected to GND.
RESET/PROG Push-Buttons
A RESET push-button is provided to allow the user to manually reset the part. When inserted, the RESET pin of the ADuC7024 is pulled to GND. Because the RESET pin on the ADuC7024 is Schmitt-triggered internally, there is no need to use an external Schmitt trigger on this pin.
To enter serial download mode, the user must hold the P0.0/BM pin low while reset is toggled. On the development board, serial download mode can be easily initiated by holding down the serial download push-button (PROG) while inserting and releasing the reset button (RESET), as illustrated in Figure 2.
Power Indicator/General-Purpose LEDs
Two general-purpose LEDs are available on the board. A red LED (LED1) is connected to P4.5 of the ADuC7024, and a green LED (LED2) is connected to P4.4. Both LEDs can be repurposed via firmware.
Breakout Header
All ADuC7024 pins are brought out to headers on either side of the board. The headers come unpopulated but can be populated using standard 0.1-inch header pins.
The thin form factor of the top of the board allows the design of an expansion board to connect above the development board, with the header pins providing both electrical and physical connections.
Firmware
Sample firmware is provided on the ADXL345 product page.
RESET PROG
RESET PROG
Figure 2. Entering Serial Download Mode to Reprogram the Board
(D) RELEASE RESET
RESET PROG
RESET PROG
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(E) RELEASE PROG
RESET
PROG
UG-065 Evaluation Board User Guide
USING THE BOARD
GETTING STARTED
The development board comes preprogrammed as a datalogger at a 100 Hz datarate. To log data, do the following:
1. Insert two AAA batteries into the battery holder.
2. Insert the MicroSD card into the slot. The card should be formatted with a FAT32 file system; most microSD cards come this way.
3. Push the on/off switch to the on position to power up the board. The red LED turns on, and the green LED blinks to indicate that the board is logging data.
4. When logging is completed, slide the on/off switch to the off position.
5. Remove the card from the slot and insert it into the card reader.
6. Insert the card reader into the USB port on your computer.
4. In the ARMWSD window, click Browse…, see encircled in Figure 3, and navigate to the location of the .hex file to be loaded onto the board. Select the file and click Open.
The acceleration log file is written to the path \XL345\DB0001.txt on the microSD card. The data in the text file consists of a set of comma-separated t, x, y, and z values, where t corresponds to time and x, y, and z correspond to the x-, y-, and z-axis acceleration data for each time point. Acceleration values are logged in LSB, where the nominal scale factor is 3.9 mg/LSB. To convert an acceleration value from LSB to mg, simply multiply by 3.9 (nominally, or measure the sensitivity of the part for a more accurate conversion).
To plot the logged data using Microsoft Excel, download the XL345DB_DataPlotter.xls file from the ADXL345 product page and follow the instructions described in the file. Users are prompted to browse to their logged data file (DBxxxx.txt), the data is imported and plotted in a new workbook, and users are then prompted to save that workbook.
PROGRAMMING THE BOARD
The board can be repurposed with no programming required using the .hex files provided on the ADXL345 product page. The .hex files are uploaded onto the board using the ARMWSD program, which can be downloaded at
ftp://ftp.analog.com/pub/MicroConverter/ARM%20Tools/AR MWSDv1.8.zip. Simply unzip the folder to a known location
and open the ARMWSD.exe file to use the program. No installation is required.
To reprogram the board, use the cable provided with the board and follow these instructions:
1. Download the desired .hex file from the ADXL345 product page to a known location, or locate it on your machine.
2. Open ARMWSD.
3. Click Configure… (see Figure 3) and select the Parts tab, shown in see. Make sure the ADuC7024 is selected in the
Select Part pull-down list (see Figure 4). Additionally, in the Comms tab, make sure the Baudrate is set to 115200, and the Serial Port is set to COM1, and then click OK.
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Figure 3. ARMWSD Window
Figure 4. ARMWSD Configure Window: Parts Tab
5. Connect the programming cable to the serial port on the PC and to the 4-pin header near the on/off switch on the board, matching up the corresponding pins.
6. In the ARMWSD window, click Start. The Status frame then prompts users to Press Download and pulse Reset on Hardware. Follow the illustrations in Figure 2.
7. When download is complete, click the Reset button on the evaluation board. The ARMWSD program can now be closed.
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SOFTWARE TOOLS
In addition to the ready-to-upload examples provided on the
ADXL345 product page, the development board is fully modifiable
and reprogrammable to allow for easy prototyping and firmware development. Firmware is written in C, and it is compiled for
Evaluation Board User Guide UG-065
the ADuC7024 ARM7 processor. Software suites (Keil, IAR, and GNU) for writing and compiling code are provided at
ftp://ftp.analog.com/pub/MicroConverter/ARM%20Tools/. The
firmware examples provided on the ADXL345 product page were written using Keil Microvision.
For instructions on how to install and use the software, refer to the ADuC702x MicroConverter™ GetStarted Guide at:
ftp://ftp.analog.com/pub/MicroConverter/ADuC702xV1.3/AD uC702xGetStartedv1.3.pdf.
To reprogram the board, download the ARMWSD program at
ftp://ftp.analog.com/pub/MicroConverter/ARM%20Tools/AR MWSDv1.8.zip.
With Keil Microvision installed, download the EVAL­ADXL345Z-DB Files.zip file from the ADXL345 product page Unzip this into a known directory. Navigate into the firmware folder and open DevBoardProj.Uv2. The project opens in Keil Microvision and allows users to modify and recompile the program.
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BOARD LAYOUT AND SCHEMATICS
See the ADXL345 product page for electronic versions of the layout and schematic files.
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Figure 5. ADXL345 Development Board Schematics
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Figure 6. ADXL345 Development Board Layout
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ESD CAUTION
Evaluation boards are only intended for device evaluation and not for production purpo ses. Evaluation boards ar e supplied “as is” and w ithout warranties of any kind, express, implied, or statutory including, but not l imited to, any implied warranty of merchantability or fitness for a part icular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of evaluation boards. Information furnished by Analog Devices is believed to be accurate and re liable. However, no responsibility is a ssumed by Analog Devices for its use, n or for any infringements of patents or other rights of third parties that may result from its use. Analog De vices re serves the right to change devices or specifications at any time wi thout notice. Trademar ks and registered trademarks are t he property of their respective owne rs. Evaluation boards are not authorized to be used in life support devices or systems.
©2010 Analog Devices, Inc. All rig hts reserved. Trademarks and registered trademarks are the property of their respective owners. UG08658-0-2/10(0)
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